Biomass refining (or biorefining) has become more prevalent in industry. Cellulose fibers and sugars, hemicellulose sugars, lignin, syngas, and derivatives of these intermediates are being utilized for chemical and fuel production. Indeed, we now are observing the commercialization of integrated biorefineries that are capable of processing incoming biomass much the same as petroleum refineries now process crude oil. Underutilized lignocellulosic biomass feedstocks have the potential to be much cheaper than petroleum, on a carbon basis, as well as much better from an environmental life-cycle standpoint.
Lignocellulosic biomass is the most abundant renewable material on the planet and has long been recognized as a potential feedstock for producing chemicals, fuels, and materials. Lignocellulosic biomass normally comprises primarily cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are natural polymers of sugars, and lignin is an aromatic/aliphatic hydrocarbon polymer reinforcing the entire biomass network. Some forms of biomass (e.g., recycled materials) do not contain hemicellulose.
In recent years, the GreenPower+® technology has been developed by American Process, Inc. (API). GreenPower+® technology is a patented technology for the production of low-cost sugars from the hemicelluloses of any type of biomass, including hardwoods, softwoods, and agricultural residues. The GreenPower+® process produces low-cost C5 and C6 sugars from the hemicelluloses of biomass feedstocks. These sugars are co-produced along with biomass power, pellets, or pulp. Essentially, sugars are extracted from the solids which are then utilized for existing applications, in synergy with pulp mills, pellet mills, biomass-based renewable power plants, and many other existing sites. Value is added while minimizing capital costs for commercial implementation, which may be retrofits, capacity additions, or greenfield sites. When applied to a corrugated medium pulping operation, the GreenPower+® technology is also known as GreenBox+® technology.
It would be desirable to retrofit existing pulp mills with a GreenBox+® process. The revenue obtainable from the sugar stream can significantly improve the economics of a pulp and paper mill. Ideally, an initial extraction and recovery of sugars is followed by a pulping process that produces a pulp product with equivalent or similar properties, or potentially even better properties for certain downstream products. Besides sugars, other co-products become possible, in particular acetates since hemicellulose has a high concentration of acetyl groups that are released as acetic acid during sugar extraction.
In addition to the potential for higher revenue, there is also potential for reduced costs. For example, if the GreenBox+® process can replace a chemical pulping method, the chemical recovery cycle may be eliminated. There may also be environmental compliance benefits and reduced costs for compliance.
Despite being the most available natural polymer on earth, it is only recently that cellulose has gained prominence as a nanostructured material, in the form of nanocrystalline cellulose (NCC), nanofibrillar cellulose (NFC), and bacterial cellulose (BC). Nanocellulose is being developed for use in a wide variety of applications such as polymer reinforcement, antimicrobial films, biodegradable food packaging, printing papers, pigments and inks, paper and board packaging, barrier films, adhesives, biocomposites, wound healing, pharmaceuticals and drug delivery, textiles, water-soluble polymers, construction materials, recyclable interior and structural components for the transportation industry, rheology modifiers, low-calorie food additives, cosmetics thickeners, pharmaceutical tablet binders, bioactive paper, pickering stabilizers for emulsion and particle stabilized foams, paint formulations, films for optical switching, and detergents.
Biomass-derived pulp may be converted to nanocellulose by mechanical processing. Although the process may be simple, disadvantages include high energy consumption, damage to fibers and particles due to intense mechanical treatment, and a broad distribution in fibril diameter and length.
Improved processes for producing nanocellulose from biomass at reduced energy costs are needed in the art. Also, improved starting materials (i.e., biomass-derived pulps) are needed in the art for producing nanocellulose. It would be particularly desirable for new processes to possess feedstock flexibility and process flexibility to produce either or both nanofibrils and nanocrystals, as well as to co-produce sugars, lignin, and other co-products. For some applications, it is desirable to produce nanocellulose with high crystallinity, leading to good mechanical properties of the nanocellulose or composites containing the nanocellulose. For certain applications, is would be beneficial to increase the hydrophobicity of the nanocellulose.
There is also a need in the art for increasing the strength of weak cellulose fibers, and improving certain properties of paper, corrugating medium pulp, and pulp products.